RentHop is expanding nationally, putting it toe to toe with a handful of other rental sites that offer countrywide coverage, including Apartments.com, Apartment List, Zillow-owned HotPads and Trulia’s rental marketplace.

What RentHop says sets it apart from the pack is its listing ratings system, which assigns scores to listings that are designed to help consumers gauge whether a listing is worth inquiring about. “HopScores” are based on the completeness of a listing, its quality relative to nearby listings and the historical responsiveness of its property manager.

RentHop screen shot.

But the scores also reflect freshness. As traffic to a listing increases, its score decreases, pushing it farther down in search results, so consumers see the newest listings first.

RentHop, which launched in 2009 and is a graduate of the Y-Combinator startup accelerator program, is also among a slew of other sites that claim to effectively guard against or weed out duplicate or fraudulent listings.

Renters have long bemoaned the swarms of dubious listings on Craigslist, but the problem also afflicts other major sites.

Trulia recently brought the scope of it into focus. The site sought to address the problem of multiple brokers posting the same listings (thereby producing duplicates) in New York City — where, due to the nature of the market, the practice is ubiquitous.

To solve the problem, it consolidates all duplicates (which it receives through brokerage listings feeds) of the same NYC listing into one single listing that displays all the different brokers that represent it.

In launching Trulia Open Markets, it chopped its New York City listing inventory in half.

Translation: Half of its previous NYC listings were duplicates.

Another differentiating feature of RentHop, which previously covered only New York City, Boston and Chicago, may be its communication tool. The tool lets consumers schedule viewings with brokers and property managers and manage responses.

Agents, brokerages and property managers may post listings to RentHop for $2 apiece (another reason why the site says it doesn’t have shady listings). They can pay in Bitcoin if they want.